Catalytic conversion process to produce highly paraffinic waxes and highly aromatic oil



E'. M. FAUBR El' AL April 14, 1970 3,506,563

CATALYTIC coNvERsIoN PRocEss To PRODUCE HIGHLY PARAFFINIC wAxEs AND HIGHLY ARoMATIc OIL .Filed Jan. 11, 1968 o@ QQ ok om.

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INVENTORS.

Rm ES BU MA FR MK E NI ER GU UA EM United States Patent O U.S. Cl. 208-24 7 Claims ABSTRACT OF THE DISCLOSURE Gas oils may be profitably treated to produce a combination of highly parafiinic waxes suitable for packaging and like uses, and highly aromatic oil suited for use as heat transfer media and the like. Gas oil is catalytically cracked to produce distillate fractions and the resulting bottoms, known as clarified oil, are distilled to obtain a heart cut boiling in the range of about 650 to 850 F. The clarified oil heart cut is dewaxed to provide a superior heat transfer oil and a slack wax, which upon solvent deoiling and percolation through an absorbent medium, produces a highly n-paraffinic wax. A high desirable wax with n-paraiiins approaching 100% may be obtained by selecting a narrower boiling point range cut of the clarified oil.

This application is a continuation-in-part of applicants copending application Ser. No. 621,937, filed Mar. 9, 1967 now abandoned.

This invention relates to the preparation of crystalline waxes from mineral oils, and the waxes are of such com position that certain desirable propertiesy are realized. In another aspect, the invention relates to the manufacture of crystalline waxes of greater n-paraffin content than waxes most often obtained from mineral oils. In still another aspect, this invention also relates to a process for the preparation of aromatic heat transfer oils.

The major portion of parafiin wax produced today is consumed by the food industry as a material for coating, impregnating,`or laminating paper, paperboard or other sheet materials. These paper materials are usually used as wrappersbags, cartons. cups, tubs, or other styles of container or covering for perishable goods. In order to perform effectively in vthese various specialized end uses it is highly desirable that the composition ofthe parafiin waxes be so controlled that a wax intended for a specific use will afford the properties required. For example, wax may be used to coat the outer wrapper on a carton of food which is offered for sale in a retail food store, and the waxed wrapper usually serves several functions. It minimizes passage of water vapor into or out of the packaged food, thus prolonging storage life or useful shelf life. The printing on the wrapper identifies the product. Gloss imparted by the wax film enhances the appearance of the wrapper, amplies colors in the printed design, and increases sales appeal of the product. Good gloss increases the attractiveness and sales appeal of such 3,506,563 Patented Apr. 14, 1970 diverse items as waxed paperboard cartons for butter and bacon, paper bags for potato chips, and waxed paper for general household purposes. It is usually important that the wax film have certain other properties including adequate resistance to blocking and scuffng, and lowest possible water vapor permeability. Good sealing strength, paper penetrability, and translucency also may be important attributes of the wax.

In the waxing of paper or paperboard, various techniques, waxing conditions, and types of machines are used to obtain maximum gloss. Naturally, the choice of equipment and conditions of operation are largely dependent on the particular job to be done. The various techniques which can be successfully used are largely dependent on the particular job to be done. The techniques which can be successfully used are well known to those concerned and they will not be described here, except to comment on the following critical features common to all. Regardless of the details of the operation, a film of molten wax is applied and this film is quenched or cooled very rapidly to a temperature Well below the wax secondary transition temperature, usually to room temperature or below. This solidies the wax while the molecules are still in a relatively unoriented state much as exists in the molten phase. Some crystal growth takes place, of course, but growth of individual crystals is greatly restricted. This results in a relatively amorphous, glasslike film of good transparency which exhibits relatively high gloss provided it has been laid down in sufiicient thickness on the proper quality substrate. After the glossy wax film has been laid down on the substrate, some recrystallization commences. The nature of this recrystallization determines whether the wax film will exhibit good or poor gloss stability.

Most paraffin Waves of commerce which are used for surface coatings, or combined impregnations and surface coatings, in applications where gloss is important are predominantly n-paraflinic in composition because a high non-normal parain content does not permit the degree of hardness, blocking resistance and scuff resistance typically required.

The general methods by which refined crystalline paraffin waxes, both of the. normal or straight chain type and the isoparafiinic or non-straight chain type, are produced from crude petroleum are well known by virtue of many publications and will not be described in detail here. Ordinarily the waxes are removed from the heavier distillate fraction of petroleum by some type. of low tem. perature separation usually a so-called solvent dewaxing process. The distillates may or may not be de-aromatized prior to dewaxing. The resulting slack waxes are further processed to remove oil and low melting components by solvent deoiling or sweating or by a combination of these methods. The waxes produced in the foregoing manner are predominantly n-parafins, but also contain a substantial proportion of non-normal parains. In addition, such waxes frequently are unsatisfactory because of poor color characteristics which can be improved, but only at expensive loss of considerable product.

Thus it is the object of this invention to obtain a crystalline wax wherein the presence of non-normal paraffins is minimized. Conversely, it is an object of this invention to obtain a crystalline wax wherein the n-paraflin content is maximized. More particularly, it is an object of this invention to provide a process whereby crystalline waxes are obtained wherein the n-paraffin content approaches one hundred percent more nearly than prior art waxes derived from mineral oils.

It is a further object of the present invention to provide a process whereby a highly aromatic oil is produced suited for use as a heat transfer medium or the like.

The foregoing objects are realized in the process of the instant invention which comprises separating wax from fractionated clarified oil produced in a particular manner. Clarified oil is a product of the catalytic cracking of mineral gas oil to produce gasoline and cracked gas oils known as cycle oils. The bottoms from the distillation of the cracked hydrocarbon produce, when separated from cracking catalyst particles, is known as clarified oil.

Catalytic cracking is ordinarily employed to increase gasoline production from mineral oils. Gas oils include fractions of crude mineral oil boiling above the ordinary gasoline range, i.e., the gas oils boil primarily in the range of about 400 to about 1100 F., and are the usual feedstock along with cycle oils for the catalytic cracking processes. The gas oil mixed with cycle oil is contacted with a natural or synthetic silica-based catalyst, e.g. silicaalumina or crystalline aluminosilicate, at elevated temperatures, e.g. about 800 to 950 F., to provide useful amounts of light gases, gasoline, cycle oil, and slurry oil. The catalytic cracking processes are well known in the art and will not be further detailed here. The bottoms produced in the catalytic cracking when settled or otherwise treated to remove entrained non-hydrocarbon materials, such as suspended solids from the catalyst are known as clarified oils.

In the present invention, it has been found necessary to feed to the cracking zone a feedstock having a minimum of about 15 weight percent cycle oil based on virgin gas oil so that a substantially greater proportion of the feed is converted to lighter material, and it is preferred that the feedstock contain at least about 30 weight percent of the recycle oil. Also in the cracking system of this invention the conversion of the feed is a minimum of about 50 weight percent, preferably at least about 60 or 62 weight percent or higher, which produces a clarified oil of an API gravity of about 25 or less, preferably about 15 or less.

The clarified oil formed from our catalytic cracking operation contains more aromatics and less non-normal parafinic materials than the heavy crude oil fractions from which crystalline petroleum waxes are ordinarily obtained. There is, however, still a significant proportion of non-normal parafiinic material which appears in wax obtained from the clarified oil. When the clarified oil is distilled or fractionated, however, the non-normal paraffinic component is found to reside in the heavier fractions and bottoms, while the lighter fractions contain waxes approaching nearly one hundred percent n-paraffin content. Thus, the waxes are provided in the present invention by distilling the clarified oil into a heart cut boiling primarily in the range of about 650 to 850 F. or into boiling range fractions containing waxes of the desired melting point, and the waxes can be recovered by conventional recovery methods of solvent dewaxing and solvent deoiling. To avoid excessive non-normal parafiinic material in the waxes, it is necessary when distilling the clarified oil to retain a bottoms fraction of a minimum of about weight percent, preferably up to about 20 weight percent oreven more. It has been found unnecessary in the present process to remove aromatic materials from the clarified oil before recovery of the wax.

The clarified oil distillate fraction is then solvent dewaxed by conventional processing techniques to provide a wax-free, highly aromatic oil and an unfinished paraffinic wax. The wax may be finished by conventional sweating or solvent deoiling procedures. Percolation through an absorbant, such as, for instance, activated bauxite and the like, results in a finished wax having a Saybolt Color of 30+, i.e. a colorless wax.

The colorless wax will have a much higher n-parafiin content than waxes produced by other processes. The nparafiin content has been found to be related to the conversion level in the catalytic cracking step, as indicated by the API gravity of the clarified oil. The highest nparaffin content results from conversion levels of at least about 60 or 62 weight percent or higher producing a clarified oil having an API gravity of less than about 15, while conversion levels of at least about 50 percent, producing a clarified oil of about 25 or less API gravity have somewhat greater amounts of branched paraffins, but are superior to the waxes of the prior art.

The dewaxed aromatic oil produced in the process of the present invention has been found to be excellently suited for use in many applications, particularly as a heat transfer oil. A good heat transfer oil must be relatively low in paraffins, e.g. less than about 45 weight percent, preferably about 15 to 30, and most preferably less than about 25 weight percent parafiins, to avoid thermal cracking in use. In order to reduce fire hazard, the fiash and fire points should be relatively high, e.g. above about 375 F. and 450 F., respectively. Low viscosity, such as for example, from about 100 to 200 SSU at 100 F., is another desirable characteristic, to provide thinner films in use and increasing the heat transfer rate. Pumping is, of course, easier for low viscosity materials. The aromatic oils produced in the process of the present invention generally have less than about 45, preferably less than about 25 weight percent parafiins, as indicated by VPC analysis, compare excellently with commercial heat transfer oils in all these characteristics, and are, in many cases, superior.

EXAMPLE I A gas oil fraction boiling between 400 and 1100 F. from a mixed base crude was catalytically cracked over a silica-alumina catalyst at 935 F. and a pressure of 10 p.s.i.g. The cracked efiiuent gas oil was recycled in an amount of 33% based on virgin gas oil to obtain a feed conversion of 63% by weight. The bottoms fraction obtained was clarified by settling to obtain a clarified oil. The oil had an API gravity of 14.2. The clarified oil was then fractionated and crystalline wax obtained as indicated in Table I.

For comparison with the waxes obtained in the process of the invention, waxes were obtained as indicated in Table I from a Mid-Continent crude fraction and from a heart cut of clarified oil of 16.2 API gravity.

The waxes obtained were compared for n-parafiin content. A very simple and reliable method for measuring relative n-parafiin content of crystalline waxes is based on the refractive index-melting point relationship. The lower the refractive index for a given melting point, the more nearly the n-parafiin content of the wax approaches 100%. The data obtained in Table I are plotted in the drawing with a base curve of refractive index at C. vs. A.S.T.M. melting point of pure n-paraffins. It will be observed that the crystalline waxes of the process of the present invention approach the 100% pure n-paraffn curve significantly more nearly than the waxes obtained from the conventionally refined crude oil fraction. It will further be observed that the wax Obtained by taking a heart cut of the 16.2 API clarified oil, is superior to the conventionally refined parain wax. Note that the wax obtained from the bottoms fraction of the clarified oil forms no part of the present invention.

From 14.2 API Clarified Oil 10-20 20-30 v30-40 40-50 v20.5 y 19.9 19.4 19.1 ASTM Vacuum Dis Range. -95% Overhead, F 556-694 616-739 609-760 629-782 Dewaxing Conditions:

Solvent 50/50 ME K-Toluene Filter and Wash Temp., F 0 0 0 0 1st Pass Deoiling Conditions:

Solvent 50/50 ME K-Toluene Filter and Wash Temp., F +40 +40 +40 +40 2nd Pass Deoiling Conditions:

olvent 50/50 ME K-Toluene Filter and Wash Temp., F +50 +50 +50 +50 Laboratory Tests:

ASTM Melting Point, F.2 114. 7 124. 0 130. 0 134.1 Refractive Index at 80 0.3-.' 1.4228 1.4250 1. 4264 1. 4273 From 16.2 API Clarified Oil From Mid-Continent Crude (On phenol-treated raffinate from a lube distillate) 0 50/50 MEK-Toluene 50/50 Mlll-Toluene 50/50 ME K-Toluene 50/50 ME K-Toluene +40 +30 +45 +40 50/50 ME KToluene 50/50 ME K-Toluene +50 +50 +50 +50 1 Bottoms.

i ASTM shows repeatability. and reproducibility to bc 0.2 and 0.6 F., respectively. 3 ASTM shows repeatability, reproducibility and accuracy of test all to be 0.00006.

EXAMPLE II The heavy gas oil and the -80 volume percent heart cut of clarified oil described in Example I were treated as follows:

Heartcut Heavy This comparison shows the product wax still testing a colorless Saybolt Color after 96 b./t. percolation yield while the regular wax color has dropped to +25 Saybolt Color after only 32 b./ t. yield.

Clarified Gas Oil Oil 25 Solvent Dewaxing (Using -50 ME K-Toluene): EXAMPLE II ilultiosis) Ratio I 'as atio gliltrvnd Bgmlralergture, 12glai- The heavy gas oil of Example II was treated as indiac ax slack wax, Perceit ca -k T 1 1.23 15.8 30 cated below to prov1de an aromatic orl suited for use as Doulilliglsngufi 5 5g I uene)' as heat transfer medium. A comparison of the products as ato St PSS Fllitlr anddxshhTrFmp" o ig of runs A, B and C with a commeiclal heat transfer oil nd ass er an as emp. DDo wax As'rM Mr., 135. 4 140. 7 1S also gwen below m Table H' DDO, Percent Oil 0. 15 0. 01

TABLE II Commercial Heat trans- Run A Run B Run C fer Oil Cat Cracking Conversion, vol. percent 61. 9 70. 2 76. 8 Yield of Clarified Oil, Vol. percent 5. 2 6. 1 5.3 Teston flarfigil: 16 2 8 l ravi y, Boiling Range, F., IBF-95% 423-970 507-972 Distillation of Clarified Oil:

Overhead Yield, Vol. percent 20 9. 5 Heart Cut Yield, Vol. percent 58.0 Bottoms Yield, Vol. percent 25 32. 5

Dewaxing of Heart Cut:

Solvent 50-50 Vol. percent ME K-Toluene Solvent/Oil Ratio:

ilution. 3/1 3/1 Wash 2/1 2/1 Filter and Wash Temp., F -5 -5 Yields:

Dewaxed Heart Cut,Vo1. percent 80. 3 86. 4 Slack Wax, V01. percent 19. 7 13. 6 Tests on Final Products:

Flash, COC, F 400 385 Fire, COC, F 460 450 Viscosity at 100 F., SSU 172 106 Viscosity at 210 F., SSU 40. 0 38. 5 Chromatographic Analysis (Silica Gel Procedure):

Saturatcs, Wt. percent 42. 9 29. 9 Aromatics, Wt. percent 53. 2 57. 6 Polars, Wt. percent 3. 9 2. 5 Boiling Range, F., 5-95 percent G60-850 653-820 1 At 60 percent.

The unfinished wax was then percolated through percolation grade Porocel clay calcined 4 hours at 700 F. Percolation temperature was 190 F. at a rate of 0.37 bbL/ton/hour. The following comparison between the regular wax color and the wax color using the improved method show the superior nature of the improved method:

Regular Method A comparison of the products of the present inventive process with the commercial product shows that in severalrespects, the products of runs A, B, and C are superior.

We claim:

1. A process for producing crystalline petroleum waxes of high n-paraiin content and a highly aromatic oil comprising the steps of catalytically cracking a feedstock consisting essentially of virgin mineral gas oil and about 15 to 30 weight percent of cracked gas oil based on said virgin gas oil, until at least about 50 weight percent of the total gas oil feed is converted to lower boiling materials, recovering a bottoms slurry oil from the efiiuent of the cracking step, clarifying said slurry oil, distilling the resulting clarified oil having an API gravity of up to about 25 to obtain a distillate containing wax of desired melting point and a residual fraction of at least about l0 weight percent of the clarified oil, and recovering a highly n-paranic crystalline wax and a highly aromatic oil from said distillate.

2. The process of claim 1 wherein the clarified oil distillate is fractionated to provide a wax of narrow molecular weight range.

3. The process of claim 1 wherein the residual fraction of the claried oil is at least about twenty weight percent.

4. The process of claim 1 wherein said clarified oil has an API gravity of up to about 15.

5. The process of claim 1 wherein said gas oil feed is cracked until at least about 62 weight percent of the total feed is converted to lower boiling materials.

6. The process of claim 1 wherein said aromatic oil contains less than about 25 weight percent parains and has a ash point above about 375 F., a lire point above about 450 F., and a Saybolt viscosity at 100 F. of from about 100 to 200 seconds.

7. The process of claim 1 wherein the clarified oil is distilled into a heart cut boiling in the range of about 650 to 850 F.

References Cited UNITED STATES PATENTS 2,890,963 6/ 1959 Fear 208-96 3,247,096 4/ 1966 Conwell 208-18 HERBERT LEVINE, Primary Examiner .U.S. Cl. X.R. 

